1. Field of the Invention
The present invention relates to a pressure sensitive adhesive composition, a pressure sensitive adhesive sheet, and an article adhered thereto. More particularly, the present invention relates to an acryl-based solvent-type pressure sensitive adhesive composition which can reduce an amount of formaldehyde generated by heating.
2. Description of the Related Art
An article adhered by a pressure sensitive adhesive composition has excellent properties in weather resistance, durability, heat resistance, low-temperature resistance, water resistance, or the like, and thus is widely used as a double-sided sticky tape, a foam tape, or the like in applications as a building material, household electrical equipment, wallpaper, airtight tape, masking tape, or the like. As the pressure sensitive adhesive composition used in such an adhered article, a solvent-type pressure sensitive adhesive composition containing acryl-based resin as a main component is used.
Further, it is supposed that the adhered article as above is used in a room of a house. In these cases, some components contained in the pressure sensitive adhesive composition may vaporize and float in air of the room. In such vaporizing substances, formaldehyde, toluene, or other chemical substances may be contained. Such chemical substances are regarded as a cause of the so-called “sick-house” syndrome.
The “sick-house” syndrome can be prevented if a pressure sensitive adhesive composition not containing chemical substances which cause such a syndrome is used for the adhered article placed in a room.
Even if the substances which may cause “sick-house” syndrome are not used, however, formaldehyde is contained in the atmosphere, and formaldehyde in the atmosphere may possibly be trapped in the pressure sensitive adhesive composition. Further, formaldehyde may be also generated by heating. Thus, it is difficult to control formaldehyde.
As a method of decreasing formaldehyde, Japanese Unexamined Patent Publication No. 2-232279 discloses the use of a formaldehyde trapping agent selected from a group consisting of urea, acetyl acetone, and a combination of urea and a promoting agent selected from a group consisting of glyoxal and acetyl acetone, and Japanese Unexamined Patent Publication No. 11-197501 discloses the use of an aldehyde adsorbent agent comprising an active energy ray-curable resin containing an acetoacetyl group. Further, it is known to use urea, thiourea, ethylene urea, dicyanediamide, glyoxalmonourethane, amines, or amides as a trapping agent.
However, ureas are not soluble in a solvent-type pressure sensitive adhesive composition. Further, dicyanediamides or amines easily react with a base component of the solvent-type pressure sensitive adhesive composition, and thus, the pressure sensitive adhesive composition exhibits a poor stability with age when dicyanediamides or amines are used.